This invention relates to an olefin stream and a method of making and using the olefin stream. In particular, the invention relates to dimerizing or oligomerizing an olefin stream using a nickel based catalyst, and optionally, hydroformylating, the dimerized or oligomerized olefin stream.
Olefin streams containing predominantly C3 to C5 olefins have been used as feed for oligomerization units. Such units are particularly useful for forming dimers as well as oligomers, the terms dimer and oligomer being used interchangeably herein. The dimers and oligomers can be converted to a variety of alkanes, aldehydes, alcohols and acids.
The formation of the dimers or oligomers is conventionally accomplished by catalytic reaction. Catalysts used in the reaction are typically nickel based catalysts or acid type catalysts.
Cosyns, J. et al., in xe2x80x9cProcess for upgrading C3, C4 and C5 olefinic streams,xe2x80x9d Pet. and Coal, Vol. 37, No. 4 (1995), describe a nickel based catalyst system known as the Dimersol(copyright) process. This process is useful for dimerizing or oligomerizing a variety of olefin feeds. In particular, the process is useful for dimerizing or oligomerizing propylene, butylene and pentylene streams.
U.S. Pat. No. 6,049,017 to Vora et al., describes the dimerization of a predominantly n-butylene containing feed stream. The n-butylene feed stream is ultimately derived from an olefin stream containing a variety of butylenes produced by a methanol to olefins reaction unit. The butylene stream from the methanol to olefins unit is pretreated by a combination of partial hydrogenation of dienes and isobutylene removal by way of an MTBE process, before sending the resulting n-butylene stream to the dimerization unit.
Nickel based catalysts, such as that described by Cosyns, are particularly good for obtaining dimers having a low degree of branching. However, these catalysts are particularly sensitive to deactivation by sulfur, nitrogen, and chlorine atoms. Since these atoms are commonly present in a variety of compounds in untreated olefin feed streams, the feed streams require a substantial amount of treatment in order to remove the poisonous sulfur, nitrogen and chlorine containing compounds.
Dimers and/or oligomers which are mono-olefins, and have a low degree of branching are highly preferred. Low branching can be considered a combination of both normal olefins and mono-branched olefins, particularly mono-methyl branched olefins. However, as shown in Vora, the preferred dimers and/or oligomers are conventionally obtained only after significant pretreatment of the olefin feed stream.
As the prior art references have shown, conventional methods of dimerizing and/or oligomerizing olefin feed stream to obtain desirable products have required a significant amount of pretreatment. It is desirable, therefore, to reduce the amount of required pretreatment without sacrificing the linear quality of the dimer and/or oligomer product.
This invention provides a method for obtaining a dimerized or oligomerized olefin product without using a significant amount of feed pretreatment. The product can be obtained without having to use additional means of hydrogenation or isoolefin removal, yet maintaining relatively low branching characteristics. The dimerized or oligomerized product is optionally converted to a hydroformylated product.
Specifically, the invention is directed to a method of dimerizing or oligomerizing an olefin which comprises contacting oxygenate with an olefin forming catalyst to form an olefin product. A propylene, butylene or pentylene containing stream is separated from the olefin product which contains at least 50 wt. % propylene, butylene, pentylene, or a combination thereof, and the separated olefin stream contains not greater than 1 ppm by weight sulfur calculated on an atomic basis and 0.5 to 10 wt. % isoolefin. The separated olefin stream is contacted with a nickel based oligomerization catalyst to form a dimer or oligomer product.
In another embodiment the foregoing method is followed, except the olefin forming catalyst is a silicoaluminophosphate catalyst.
In another embodiment, the separated olefin stream comprises not greater than 1 ppm by weight nitrogen. In yet another embodiment, the separated olefin stream comprises not greater than 0.5 ppm by weight chlorine. In still another embodiment the isoolefin is isobutylene.
The silicoaluminophosphate catalyst, according to one embodiment, is made from SAPO-34 or SAPO-18 molecular sieves, or a combination thereof. Preferably, the silicoaluminophosphate is an intergrowth of SAPO-34 and SAPO-18 or ALPO-18.
According to one embodiment, the dimer or oligomer product is recovered and contacted with a hydroformylating catalyst to form a hydroformylated product. According to another embodiment, the hydroformylated product is converted to an acid or alcohol. Alternatively, the acid or alcohol is converted to an ester, if desired. The ester is optionally added to a polymer composition.
The invention is also directed to an olefin composition. The composition, according to one embodiment, comprises at least 50 wt. % propylene, butylene, pentylene or a combination thereof, and contains not greater than 1 ppm by weight sulfur, not greater than 1 ppm by weight nitrogen, and not greater than 0.5 ppm by weight chlorine, each calculated on an atomic basis, and 0.5 to 10 wt. % isoolefin. The isoolefin is preferably isobutylene.
The invention further provides a method of converting an oxygenate to a hydroformylated product. The method comprises contacting oxygenate with a silicoaluminophosphate molecular sieve catalyst to form an olefin product, and separating a propylene, butylene or pentylene containing olefin stream from the olefin product, wherein the separated olefin stream comprises at least 50 wt. % propylene, butylene, pentylene, or a combination thereof, and the separated olefin stream contains not greater than 1 ppm by weight sulfur calculated on an atomic basis, and 0.5 to 10 wt. % isoolefin. The separated olefin stream is contacted with a nickel based oligomerization catalyst to form a dimer or oligomer product; and the dimer or oligomer product is contacted with a hydroformylating catalyst to form a hydroformylated product.